Improve workflow tests robustness

[Blast545]

Attempts to fix #58, WIP

Summary

Before trying to change the underlying virtual buffer used to run GUI tests, this PR changes the arguments passed to the after_make.sh script to make it more robust.

This is already done in gz-rendering, see: gazebosim/gz-rendering#255

Running CI a couple of times before asking for reviews.

Checklist

• Signed all commits for DCO
• Added tests -> potentially fixes tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

[codecov]

Codecov Report

Merging #419 (4a521b8) into ign-gui3 (c7bfb8a) will not change coverage.
The diff coverage is n/a.

❗ Current head 4a521b8 differs from pull request most recent head 672275e. Consider uploading reports for the commit 672275e to get more accurate results

@@            Coverage Diff            @@
##           ign-gui3     #419   +/-   ##
=========================================
  Coverage     65.45%   65.45%           
=========================================
  Files            29       29           
  Lines          3216     3216           
=========================================
  Hits           2105     2105           
  Misses         1111     1111           

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[chapulina]

Ohh for some reason I thought we had already applied that PR to GUI! Well spotted! CI looks unusually happy, this is a great sign! 🙏🏽

[Blast545]

I took some time to "stress test" this PR before merging to have some confidence that it improves our current state with Github Actions.

The whole history of attempts can be seen here: https://github.com/gazebosim/gz-gui/actions/runs/2506612183
Out of 5 attempts, it failed once on Bionic CI and twice on Focal CI exactly in the same place, I've opened an issue to track this error: #421

Failure on Windows is being tracked with #420, so I'll merge this PR. 🚀